Imaging of an Infalling Disklike Envelope around L1551 IRS 5
Imaging of an Infalling Disklike Envelope around L1551 IRS 5
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L1551 IRS 5 周围下落盘状包络的成像
DOI：
10.1086/178158
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
K. Sunada
中科院分区：
文献类型：
--
作者：
M. Saito;R. Kawabe;Y. Kitamura;K. Sunada
利用野边山毫米波阵对L1551 IRS 5的H_（13）CO ~+（J = 1-0）辐射进行了孔径合成观测。发现在P. A处的发射具有盘状结构，大小为5600 × 2800 Au。= 160°。如果我们假设一个几何上薄的圆盘，它的半径和倾角估计为2800 Au和60° [= cos-1（2800/5600）]，并且圆盘主轴几乎垂直于分子流出。注意到存在径向运动，即，在内部区域（r < 1000 Au）中，沿圆盘短轴的速度梯度为沿着。考虑到H13 CO+特征和双极流出之间的几何关系，该运动可以解释为下落运动，因为蓝移发射位于盘的远侧，而红移发射位于近侧。在r = 800 Au时，经倾角校正后的下落速度估计为0.6 km s-1，小于自由下落速度（0.1 km/s）。5 km s−1（r = 800 Au），恒星质量为1 M。盘的H2质量估计为0.27 M的反冲和质量的下降率分别为~1.1 × 10-5 M yr-1。除了下落运动外，分子发射还具有沿长轴沿着的速度结构，这表明有旋转运动。在r = 900 Au时，经倾角校正后的自转速度估计为0.23 km s-1，小于开普勒自转速度，表明包层没有旋转支撑。H13 CO+盘状结构是围绕L1551 IRS 5的盘状下落包层。
Aperture synthesis observations of H13CO+ (J = 1-0) emission from L1551 IRS 5 were made using the Nobeyama Millimeter Array. It is found that the emission has a disklike structure with a size of 5600 × 2800 AU at P.A. = 160°. If we assume a geometrically thin disk, its radius and inclination angle are estimated to be 2800 AU and 60° [= cos–1 (2800/5600)], and the disk major axis is almost perpendicular to the molecular outflow. It is noted that there exists radial motion, i.e., velocity gradient along the disk minor axis in the inner region (r < 1000 AU). The motion can be interpreted as infalling motion because the blueshifted emission is located on the far side of the disk and the redshifted emission on the near side by considering the geometrical relation between the H13CO+ feature and the bipolar outflow. The infalling velocity corrected for the inclination is estimated to be 0.6 km s–1 at r = 800 AU and is smaller than the free-fall velocity (∼ 1. 5 km s−1 at r = 800 AU ) with a stellar mass of 1 M☉. The H2 mass of the disk and the mass infall rate are estimated to be 0.27 M☉ and ~1.1 × 10-5 M☉ yr–1, respectively. In addition to the infalling motion, the molecular emission also has a velocity structure along the major axis, suggesting rotating motion. The rotational velocity corrected for the inclination is estimated to be 0.23 km s–1 at r = 900 AU, which is smaller than Keplerian rotational velocity, suggesting that the envelope is not rotationally supported. The H13CO+ disklike structure would be a disklike infalling envelope around L1551 IRS 5.